Certain tables, of the Prospect Tracking database, are in relation one with the others.
A good understanding of these relations is essential when using commands such as:
| · | Multi criteria search,
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| · | Quick search,
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| · | Calculated search,
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| · | Sort,
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| · | Export,
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| · | Printing.
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The advantages of a relational database are numerous and below are two of the principle ones:
| · | No unnecessary entries : time saver
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| · | No redundant information : space saver
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Naturally there is a link which associates a registration of one table to those tables in relation. It's a matter of the same field in the 2 tables. This field is none other that the relation key.
Type of relations
 | Relation 1 to N
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| A couple may have several children, and own several cars.
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| It would be more judicious to store the relative information of the children and car records in definite files, rather than in the couples file.
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| For each couple, the number of records, in relation to cars and children, can be contained between O and N.
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| It is difficult in this case to anticipate a record structure, "couple" integrated with the information 'children' and 'cars' without being at some time or other limited by the amount of anticipated information and penalising the place occupied beforehand.
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| It would be in their interest to create a 'couple' file and two related files 'children' and 'cars'. The type of relation between the file 'couple' and the files 'children' and 'cars' is 1 to N.
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| A couple may correspond N children and N cars. The 'children' and 'cars' records have been created through necessity.
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| Relation 1 to 1
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| One Contact record can correspond to one record in relation maximum.
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| A contact has one social security card and only one.
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| The large amount of information relative to this card is managed from the corresponding file.
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| In this way if the person does not own a card (a child for example) no unnecessary place has been used.
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| Relation N to N
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| Take for example, keywords: A 'contact' record can be developed in an unlimited way by these hierarchical keywords.
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| It is possible to link a 'contact record to several keywords. In the same way the same keyword can affect several 'contact' records.
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